Byssinosis is an intermittently episodic obstructive airways syndrome in cotton mill workers which can lead to chronic airways obstruction. The diagnosis and grading are based upon symptoms and the main objective data about the disease have been decreases in the forced expired volume in one second (FEV1.0). Since significant abnormalities may be present in small airways in the absence of symptoms or decreases in FEV1.0 a large population not presently identified as having byssinosis might have small airway abnormalities acutely and/or chronically as a result of the cotton dust exposure. We propose to study the incidence of chronic small airway abnormality and acute small airway reactivity in a population of cotton textile workers exposed to cotton dust. Emphasis will be placed upon that portion of the population with no symptoms of byssinosis and no demonstrable chronic or acute decrease in the forced expiratory volume in one second. Specific objectives are to: (1) determine the incidence of byssinosis in a population of cotton mill workers; (2) measure the incidence of small airway abnormalities on an episodic as well as chronic time scale in the population of cotton mill workers; (3) measure the respirable dust concentrations in each working environment; (4) determine the relationship between small airway abnormalities and large airway abnormalities in those subjects with either acute or chronic decreases in FEV1.0; and (5) correlate the incidence of small and large airway abnormalities (episodic and chronic) with respirable dust levels.